基于茎秆直径微变化信号强度监测交替沟灌玉米水分状况

为研究茎秆直径微变化信号强度与交替沟灌玉米水分状况,试验设置常规沟灌处理、交替沟灌高水处理和交替沟灌低水处理,研究了3种处理玉米茎秆直径最大日收缩量(maximum daily shrinkage,MDS)、茎秆直径日增长量(daily increase,DI)与土壤含水率的关系,探讨了以信号强度(指标实测值与参考值的比值)诊断玉米水分状况的可行性,并通过"信噪比"结合水分敏感性对各生育期内MDS信号值(signal MDS,SIMDS)与DI信号值(signal DI,SIDI)适宜性进行评价。结果表明:MDS和DI在不同生育期表现出显著差异(P0.01),易受到气象因素影响,对土壤含水率变化的响应较弱。信号强度可排除气象因素干扰,各水分处理信号值呈现出不同规律,交替沟灌玉米信号值高于常规处理信号值。不同生育期内信号强度与水分敏感性表现出显著差异,拔节期内3组处理SIDI信噪比平均值大于SIMDS,且复水后SIDI信号强度降低幅度平均值(51.44%)大于SIMDS(30.55%),因此SIDI是更适宜的拔节期水分诊断指标;抽穗期内2种指标敏感性和信噪比相差不大,SIMDS与土壤含水率相关性更好,抽穗期应选择SIMDS作为水分亏缺诊断指标。成熟期SIMDS信噪比平均值大于SIDI,复水后信号强度降低幅度平均值(65.12%)大于SIDI(52.78%),SIMDS更适宜作为玉米水分状况诊断指标。该研究可为监测交替沟灌玉米水分技术提供技术支撑。

Signal intensity of stem diameter fluctuation diagnosing alternate furrow irrigation maize water deficit

Abstract: In order to evaluate the feasibility of applying signal strength to the diagnosis of alternate furrow irrigation of maize, and find out the most suitable growth period of water deficit index, the experiment was conducted in the experiment station of Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Area of Ministry of Education, Northwest Agriculture and Forestry University from July to September in 2016. In the experiment, the treatments of conventional furrow irrigation (CFI), alternate furrow irrigation of high water (AFIH) and alternate furrow irrigation of low water (AFIL) were set, and the irrigation amounts of AFIH and AFIL were 2/3 and 1/2 respectively of CFI at every turn. The soil moisture content, stem diameter changes, air temperature, radiation and other meteorological factors were measured. Responses in maximum daily stem shrinkage (MDS) and stem daily increase (DI) to soil water content and meteorological factors were analyzed, 2 signal irrigation indices (SIMDS and SIDI, which were signal MDS and signal DI) were established, and the signal values were calculated by the ratio of measured values to reference values. The reference values were obtained by the regression equation of plant stem diameter indicators and meteorological factors under no water stress condition. However, water-stress index variability may increase with the increase of water stress; high variability index requires multiple measurements to reduce the error, which increases the cost, so the variability (noise value) of index and the intensity also should be considered. High signal value means the change of the indicators derived from stem diameter for soil moisture response is stronger, and high signal value means the variability of the indicators caused by the water difference is acceptable. When soil moisture changes, the signal-to-noise ratio (SNR) in the short term is greater, indicating that the index is more suitable for diagnosing the water status of plants. At the same time, if the large signal value changes can be recorded shortly after rehydration, then the change of stem diameter is more sensitive to soil moisture, that is, the sensitivity of the index is stronger. The SNR and the suitability of indices (SIMDS, SIDI) in each growth period were evaluated. The results showed that MDS and DI were easily affected by meteorological factors, and there was a weak response for the above 2 indices to soil water content. SIMDS and SIDI could exclude the interference of meteorological factors. The SIMDS and SIDI showed a better linear relationship with soil moisture. Stem diameter signal indicator could be used in corn moisture status diagnosis under the alternate furrow irrigation. In the different periods, signal indicator and water sensitivity showed significant differences; in jointing period, the SNR of SIDI was larger, and the decrease range of signal intensity after rehydration was greater than the SIMDS, so SIDI was more suitable for moisture diagnosis in jointing stage. In heading stage and maturity stage, the SNR of SIMDS was larger than SIDI, and the sensitivity and correlation with the soil moisture content were better than SIDI, so SIMDS was more suitable for corn moisture diagnosis in heading and maturity stage.